hmmm. just not sure if the chance is worth it but will need for bike numerous times and this once or maybe twice with the drag strip

They really aren't designed for multiple applications. I guess if your absolutely set on it, I'd go with an SA2010 with visibility you're comfortable with on the bike, provided that the "size" of the impact the M is rated for isn't more. Like I can envision the SA rated for multiple small impacts one might experience being strapped in on the B pillar or something, and the M for a single HUGE impact...flying off the bike and hitting something.